Tamping cartridge made of filled, elongated polymeric tubing

ABSTRACT

A tamping cartridge for tamping explosive charges in bore holes which consists of a sealed plastic tubing essentially filled with a finely divided solid and a wall thickness of 50 to 100 microns.

United States Patent Lewer [451*Sept. 24, 1974 [54] TAMPING CARTRIDGE MADE OF FILLED, 2,216,067 9/1940 Clark 102/21.4 X ELONGATED POLYMERIC TUBING 2,787,933 4/1957 Wester.... 86/21 3,752,079 8/1973 Lewer 102/30 Inventor: Hans Lewer, Witten-Annen,

Germany Assignee: Chemische Fabrik Kalk GmbI-I Filed: Jan. 26, 1973.

Appl. No z 327 l8l V I 7 Notice: The portion of the term of this patent subsequent to Aug. 14. 1990. has been disclaimcd.

Foreign Application Priority Data Jan. 26, 1972 Germany 2203488 US. Cl 102/30, 86/20 C, 102/21.4, 102/23 Int. Cl. F42d 1/08 Field of Search 86/20 C; 102/2l.4, 23, 102/30 References Cited UNITED STATES PATENTS 7/1880 Sager 102/21.4 X

FOREIGN PATENTS OR APPLICATIONS 1,446,964 l2/l968 Germany l02/2l.4 I,808,554 9/l970 Germany l02/2l.4

Primary Examiner-Leland A. Sebastian Attorney, Agent, or Firm-Laurence, Laurence & Neilan [57] ABSTRACT 5 Claims, 1 Drawing Figure TAMPING CARTRIDGE MADE OF FILLED, ELONGATED POLYMERIC TUBING In the mining of coal, ore or minerals as well as in the driving of galleries in underground mines, workings are still largely initiated by explosive charges. For this, bore holes are made in the rock or coal to be cleared and the explosive charges are introduced into these bore holes. For reasons of blasting technique, it is necessary after inserting the explosive cartridges, to tamp the charge, for which purpose mud preparations, the so-called gouge tamping were originally used.

For a long time, there have been endeavours in mining to reduce substantially the quantities of coal and rock dust which arise during working, since by virtue of their explosive and health-impairing effects, they constitute a serious danger to mining operations and to the persons employed therein. These endeavours have been extended to blasting, since it is during such blasting that substantial quantities of dust occur. A means widely used to resolve this problem is so-called water tamping. With this technique, lengths of plastics hosing filled with water and sealed at both ends are introduced after the explosive charge into the bore holes, the hose diameter being somewhat smaller than that of the hole. Ramming packs these lengths of hose tightly into the bore hole. Instead of the hose lengths, ampoules made from plastics material and filled with water are also used and by virtue of their shape or the form of their surface, they become jammed in and tamp the bore hole. Such water-filled plastics hose lengths or ampoules are generally described as water tamping cartridges. In order to achieve satisfactory tamping, these water tamping cartridges should have an internal pressure of at least 0.1 atm. For this reason and in order substantially to exclude the possibility of the water tamping cartridges becoming damaged during transport, the wall thickness of the casings for these cartridges should be at least 0.8 mm. When shots tamped with water tamping cartridges are fired, the casings of the water tamping cartridges are ruptured and the water contained therein becomes distributed in the form of very fine droplets in the resultant blast gases which consist of combustion gases, coal and rock dust. The water droplets which result are intended to lay the dust contained in the blasting gases and bring it to the floor of the gallery where it is incapable of flying. Furthermore, the water droplets are intended to wash the combustion gases out of the blasting gases and at least diminish the effects of these gases which are harmful to health.

In addition to these water tamping cartridges, cartridges are also used in which the water filling is thickened by a gel-forming substance into a pasty composition of approximately 95 percent water content. Since these cartridges do not have a curved shape, tamping in the bore hole and closure of the bore hole can be achieved only when the cartridge is pierced at one end. Thus, when the ram pushes the cartridge down into the hole, a little of the mixture is forced out of the cartridge, and only then can the cartridge become sufficiently deformed to fill the cross-section of the bore hole.

It has however been found that the effects intended with water or paste tamping cartridges are only achieved to a limited degree. Even the use of tamping cartridges which are filled with sodium chloride or calcium chloride solution instead of water produce only a negligible improvement in the laying of dust and gas. The use of these aqueous tamping means can, moreover, lead to a disadvantageous deterioration of the climate in the mine due to an increase in relative humidity in the mine damp.

It has therefore already been proposed in my copending application Ser. No. 51,735, US Pat. No. 3,752,079 to use tamping cartridges which are filled with finely particulate solid calcium chloride. In order to improve the dust and gas-binding action, wetting means, alkaline and/or oxidisingly acting substances may be admixed with this powdered calcium chloride. The quantities of gases and dust arising during blasting operations can be considerably reduced with these tamping means.

For the functioning of such tamping cartridges, it is essential to dispose them so firmly in the bore hole that the explosion cannot force them from the bore hole again without their breaking up. Instead, the plastics casing of the cartridge should be so ruptured that the content of the cartridge can become distributed in the explosion gases. The cartridges filled with water or with aqueous solutions therefore in many cases have a slightly curved form. By virtue of the slight excess pressure of the liquid filling and the thickness of the walls, the cartridge seeks to retain this shape. It therefore presses itself resiliently against the walls of the bore hole and is therefore retained in position.

In the case of the same tamping cartridges, filled however with finely particulate solid substances, such elasticity can only be imperfectly achieved, if at all, so that tamping of these cartridges in the bore hole repeatedly presents difficulties.

Therefore, tamping cartridges were sought which despite being filled with finely particulate solids, can easily and permanently be jammed in bore holes by being subsequently rammed. A tamping cartridge for tamping explosive charges in bore holes, particularly in underground mining workings, has been found which consists of a hose-like plastics casing filled with finely particulate solids and which is enclosed on all sides. The plastics coating has a wall thickness of about 50 to microns and the filling of finely particulate solid material does not completely fill the space inside the cartridge.

Such a thin-walled cartridge, the space inside which is not completely filled by finely particulate solid material has, in contrast to the thick-walled tightly waterfilled cartridge, no elasticity of fonn. It is flexible and can, therefore, when it is introduced into the bore hole and pressed firmly against the explosive cartridge, adapt itself to the shape and size of the bore hole. In doing so, it becomes pressed firmly against the wall of the bore hole and thereby tamped.

Cartridges in which the finely particulate solid material, with loose filling, essentially fills the volume of the cartridge, have been found to be particularly advantageous. By virtue of the loose filling of finely particulate solid, there remains between the individual particles thereof a space which is not filled by solid material and which for one cartridge as a whole, is large enough to impart the aforementioned properties to this cartridge. The space which is not filled by solid matter is hereinafter described as the empty volume.

The plastics casing can in principle be made from any plastics materials from which, without loss of tearing strength and flexibility, hose-shaped structures can be manufactured with a wall thickness of about 50 to 100 microns. Polyolefin plastics such as for example polyethylene, have been found to be particularly suitable. Other suitable plastics are for example polystyrene or polyvinylchloride.

It is furthermore also possible to manufacture the cartridge casings from parchment paper, paraffin paper or the like, so long as these materials are satisfactorily tear-resistant and flexible, but the use of plastics foil has been found to be more advantageous.

The diameter of these hose-shaped structures should be somewhat but only very slightly smaller than the diameter of the bore hole in which the explosive charge is to tamped. It has furthermore been found to be ideal for the diameter of the hose shaped structure to be somewhat larger than the diameter of the explosive charge which is to be tamped. In the case of the dimensions of currently used explosive cartridges, therefore, the diameter of the cartridge casings to be used according to the invention should be between 25 and 35 mm.

These hose-shaped casings can be sub-divided into pieces of approximately to 30 mm length and can be closed at one end for example by welding, adhesion or in some other manner. In this way, hose-shaped cartridges are formed which are closed at one end and into which then a quantity of finely particulate solids is filled which does not completely fill up the space inside the cartridge. Advantageously, such a quantity of finely particulate solids is filled into the cartridge that in the case of loose bulk filling, the space inside the cartridge is just filled. Subsequently, the filling aperture of the tarnping cartridge is likewise sealed by adhesion or welding or in some other manner.

It is however also possible to provide at the filling end of the cartridge a self-closing valve which closes automatically after the finely particulate solids have been filled into the cartridge and so reliably prevents the finely particulate solids from reemerging from the the cartridge. Valves which consist of a possibly funnelshaped portion of hose of the same diameter as the cartridge which is to be sealed and which is fitted into the closure aperture thereof, have been found to be particularly successful. The two outer edges of the valve hose and of the cartridge which is to be sealed are connected firmly to one another. It may be advantageous to provide on or in the vicinity of this joint a clamping means which is connected firmly to the cartridge and which consists essentially of two rod-shaped plastics parts which become connected firmly to the cartridge transversely to the longitudinal axis of the cartridge and in the vicinity of the filling aperture and which are so elastic that they constantly endeavour to occupy their greatest longitudinal extension.

Furthermore, it is possible to fill a longer portion of the hose which is closed at one end, with filling material, and to use a correspondingly constructed apparatus to squeeze off from the filled portion of hose cartridges 15 to 30 cm in length, whereby it must be ensured that the volume of each partial length is not completely filled by the contents. Ideally, the contents ought just to fill this volume with loose bulk. These cartridges are then likewise tightly sealed at the still-open end.

Despite their small wall thicknesses, the tarnping cartridges according to the invention, which are sealed all round, are readily storable and transportable. For application, the charge is first introduced into the bore hole together with the necessary detonating means. Then the tarnping cartridge according to the invention is introduced into the bore hole and rammed so against the charge that the tarnping cartridge is compressed and kinked at several places. This causes the kinked parts of the tarnping cartridge to be displaced obliquely to the longitudinal axis of the bore hole and to jam against the walls thereof. By virtue of the empty volume present in the cartridge, this deformation is a lasting one, so that the tarnping cartridge completely and lastingly closes the cross-section of the bore hole.

The sole FIGURE shows a diagrammatic view of a section through a bore hole 2 made in the rock 1, filled with a charge and tamped. It contains the explosive charge 3 provided with detonating means and is tamped by the tarnping cartridge 4 according to the invention. Instead of one tarnping cartridge, if necessary a plurality of tarnping cartridges can be introduced into and tamped in a bore hole.

It is however also possible and particularly advantageous for the bore hole diameter to be substantially larger than the diameter of the tarnping cartridge and for the tarnping cartridge to be applied under such pressure that it bursts at one or more places. The filling which consists of finely particulate solid substances will then emerge and, by having pressure applied to it, be so well distributed over a larger bore hole diameter that reliable tarnping is achieved.

As finely particulate solids for use as a filling for the tarnping cartridge according to the invention, particularly finely particulate calcium and/or magnesium chloride has proved successful, containing advantageously more than percent by weight of particles with a diameter of less than 1 mm and more than 60 percent by weight of particles with a diameter of less than 0.3 mm.

The water content of the calcium chloride or magnesium chloride respectively may be between 55 and 0 percent by weight, i.e., hexa-, tetra-, di-, monohydrates and practically anhydrous substances can be employed.

To render the chlorides of the calcium or magnesium more effective, wetting agents, in particular non-ionic wetting agents like alkyl-phenolpolyglycolether may be added. The addition of alkaline reacting substances such as calcium oxide, calcium hydroxide, calcium carbonate, dolomite, sodium hydroxide, sodium hydrogen carbonate, sodium carbonate, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, urea and similar substances also proved useful. Calcium chloride or magnesium chloride treated with ammonia, thus reacting alkaline, may also be used. The addition of oxidizing agents like manganese dioxide, potassium permanganate, has advantageous effects. Additionally, sodium chloride or another metal salt may be admixed with the materials introduced into the blast-holes.

The finely powdered calcium chloride or magnesium chloride apparently combine with the large amounts of water steam forming after the blast. In this way the steam is condensed much faster into water drops which contain liquid calcium chloride or magnesium chloride. This mixture is instrumental in quickly agglomerating the dust, thereby forming particles too big to reach the lungs, also precipitating the dust where it rises. It was also found that nitrous gases dissolve much better in the forming solution than in water steam or small drops that consist of water only. To increase the solubility of nitrous gases in the forming solution, additional alkaline reacting substances may be introduced into the blastholes in addition to calcium chloride or magnesium chloride. The quantities of alkaline substances may be varied for best absorption of nitrous gases. 2-10 percent of alkaline substances, contained in the material introduced into the blast-holes after the explosives, are generally sufficient to reduce, within a few minutes, the concentration of nitrous gases, contained in the air after blasts, far below the harmful limit.

A further advantage is the absorption of the precipitated dust which is retained, having been wetted by a solution of hygroscopic salts. On account of its content of hygroscopic salt the water in the precipitated layer remains bonded, preventing the dust from rising again after further blasts. This danger exists if the dust was precipitated by water only which would eventually evaporate. Moreover, humidity of air in mines will not increase if materials are used in accordance with the invention.

Increased humidity of air in mines will always be observed when water is applied in cartridges or is sprayed in the mine. However, such an increase of the relative humidity of the air leads to a higher moist temperature deteriorating thereby the quality of the air. This, of course, is not desired and especially not in warmer galleries situated at greater depth. If materials, in accordance with the invention, are introduced into blastholes, the air in mines will practically not be altered.

Because of the empty space provided in the tamping cartridges according to the invention and by virtue of the minimal wall thickness, it is now possible for tamping cartridges filled with finely particulate solids to be easily jammed in the bore holes so that the tamping lastingly seals the entire cross-section of the hole. Furthermore, in contrast to the water-filled tamping cartridge in which the greater wall thickness of the foil must definitely obviate a tearing-open of the ampoule and discharge of the contents in the bore hole, damage to the thin foil used for the tamping cartridge according to the invention and emergence of the filling into the bore hole will have little or no disadvantageous influence on the efficacy of the tamping.

What is claimed is:

l. A tamping cartridge for tamping charges in bore holes consisting of an elongated polymeric tubing closed on all sides and almost filled with finely particulate solids, said polymeric tubing having sufficient empty volume to during use permit deformation without rupture, said polymeric tubing having a thickness of about 50 to 100 microns.

2. A tamping cartridge according to claim 1 in which said finely divided particulate solids is selected from the group consisting of calcium chloride and magnesium chloride.

3. A tamping cartridge according to claim 1 in which said polymeric tubing is filled with loose bulk particulate solids.

4. A tamping cartridge according to claim 1, wherein said polymeric tubing is a polyolefin tubing.

5. A tamping cartridge according to claim 2 in which said finely divided particulate solids contain more than percent by weight of particles with a diameter less than 1 mm and more than 60 percent by weight of particles with a diameter of less than 0.3 mm. 

2. A tamping cartridge according to claim 1 in which said finely divided particulate solids is selected from the group consisting of calcium chloride and magnesium chloride.
 3. A tamping cartridge according to claim 1 in which said polymeric tubing is filled with loose bulk particulate solids.
 4. A tamping cartridge according to claim 1, wherein said polymeric tubing is a polyolefin tubing.
 5. A tamping cartridge according to claim 2 in which said finely divided particulate solids contain more than 80 percent by weight of particles with a diameter less than 1 mm and more than 60 percent by weight of particles with a diameter of less than 0.3 mm. 